Process for the preparation of ethylene copolymers

ABSTRACT

A polymerization process comprising contacting under polymerization conditions ethylene and at least one alpha olefin of formula CH2=CHA wherein A is a C 2 -C 20  alkyl radical to obtain a copolymer containing from 95% by mol to 50% by mol of ethylene derived units in the presence of a catalyst system obtainable by contacting:
         b) at least a metallocene compound of formula (I)       

     
       
         
         
             
             
         
       
         
         
           
             b) alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally 
             c) an organo aluminum compound; 
             wherein the groups R 1 -R 4 , L, M and W are described in the text.

The present invention relates to a process for the preparation ofethylene/alpha olefins copolymers wherein the process is carried out inthe presence of a metallocene based catalyst system having a particularsubstitution pattern.

WO 03/050131 describes a class of bridged bis indenyl metallocenecompounds wherein the indenyl moieties are substituted at least inpositions 2, 4 and 5. In this document about 100 pages are used to listexample of compounds included in the general formula, al these compoundsare bridged bis indenyl metallocene compounds substituted in positions2, 4 and 5. WO 03/050131 states that this class of metallocene compoundscan be used for every kind of polymerization process including solutionpolymerizations, however all the examples are directed to slurrypolymerization process.

PCT/EP2004/013827 a class of bis indenyl metallocene compounds whereinthe indenyl moieties are substituted in position 5 and 6 by a condensedring is disclosed. PCT/EP2004/013827 is mainly focused on C₁ symmetricstructures and there are no explicit disclosures of C₂ symmetriccompounds. In other words this document is focused on metallocenecompounds comprising two cyclopentadienyl moieties having differentsubstitution patterns.

EP 05103955.0 relates to a solution polymerization process for thepreparation of propylene/ethylene copolymers. This document is silentabout the preparation of ethylene higher alpha olefins copolymers.

The applicant found that by using a metallocene-based catalyst systemwherein the metallocene compound has a particular substitution patter itis possible to obtain ethylene based copolymers in high yields whereinthe copolymers are endowed with a very high molecular weight.

An object of the present invention is a polymerization processcomprising contacting under polymerization conditions ethylene and atleast one alpha olefin of formula CH₂═CHA wherein A is a C₂-C₂₀ alkylradical to obtain a copolymer containing from 95% by mol to 60% by molof ethylene derived units in the presence of a catalyst systemobtainable by contacting:

-   -   a) at least a metallocene compound of formula (I)

-   -   b) an alumoxane or a compound capable of forming an alkyl        metallocene cation; and optionally    -   c) an organo aluminum compound;    -   wherein in the metallocene compound of formula (I):    -   M is an atom of a transition metal selected from those belonging        to group 3, 4, or to the lanthanide or actinide groups in the        Periodic Table of the Elements; preferably M is zirconium,        titanium or hafnium;    -   X, equal to or different from each other, is a hydrogen atom, a        halogen atom, a R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group        wherein R is a linear or branched, cyclic or acyclic,        C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,        C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical; optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; and R′ is a C₁-C₂₀-alkylidene,        C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or        C₇-C₂₀-arylalkylidene radical; preferably X is a hydrogen atom,        a halogen atom, a OR′O or R group; more preferably X is chlorine        or a methyl radical; L is a divalent bridging group selected        from C₁-C₂₀ alkylidene, C₃-C₂₀ cycloalkylidene, C₆-C₂₀        arylidene, C₇-C₂₀ alkylarylidene, or a C₇-C₂₀ arylalkylidene        radicals, optionally containing heteroatoms belonging to groups        13-17 of the Periodic Table of the Elements, or it is a        silylidene radical containing up to 5 silicon atoms; preferably        L is Si(R₁₁)₂ wherein R₁₁ is a linear or branched, cyclic or        acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,        C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical; more        preferably L is Si(CH₃)₂ or SiPh₂;    -   R₁ is a linear C₁-C₄₀ hydrocarbon radical optionally containing        heteroatoms belonging to groups 13-17 of the Periodic Table of        the Elements such as methyl or ethyl radical or an alpha        branched aryl or arylalkyl radical containing from 2 to 20        carbon atoms optionally containing O, N, S, P and Se atoms, in        particular O, N and S atoms such as 2(5-Me-thiophenyl) or        2(5-Me-furanyl) radicals; preferably R₁ is a linear        C₁-C₂₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl radical, optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; preferably R₁ is a linear C₁-C₁₀-alkyl        radical; more preferably R₁ is a methyl, or ethyl radical;    -   R₂ and R₃, equal to or different from each other, are C₁-C₄₀        hydrocarbon radicals optionally containing heteroatoms belonging        to groups 13-17 of the Periodic Table of the Elements or R₂ and        R₃, are part of 4-7 membered ring condensed to the benzene ring        of the indenyl moiety said ring optionally containing        heteroatoms belonging to groups 13-17 of the Periodic Table of        the Elements; the valence of each atom forming said ring being        substituted with R₁₈ radicals; that means that it is filled with        R₁₈ groups, wherein R₁₈, equal to or different from each other,        are hydrogen atoms or a C₁-C₂₀ hydrocarbon radical; preferably        R₁₈ is a hydrogen atom or a linear or branched, cyclic or        acyclic, C₁-C₂₀-alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl,        C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radical,        optionally containing one or more heteroatoms belonging to        groups 13-17 of the Periodic Table of the Elements; more        preferably R₁₈ is a hydrogen atom or a linear or branched,        C₁-C₂₀-alkyl radical; more preferably R₁₈ is a hydrogen atom or        a methyl or ethyl radical; said ring can be saturated or it can        contain double bonds; preferably R₂ and R₃, equal to or        different from each other, are linear or branched, cyclic or        acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,        C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical        optionally containing heteroatoms belonging to groups 13-17 of        the Periodic Table of the Elements or R₂ and R₃ are part of a 5        or 6 membered ring; said ring optionally containing heteroatoms        belonging to groups 13-16 of the Periodic Table of the Elements        preferably groups 15-16 of the Periodic Table of the Elements;        the valence of each atom forming said ring being substituted        with R¹⁸ radicals; as described above; preferably R² and R³, are        C₁-C₂₀ alkyl radicals or form together a condensed saturated 3-7        membered ring;    -   R⁴ is a hydrogen atom or a C₁-C₄₀ hydrocarbon radical optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; preferably R⁴ is a hydrogen atom or a        linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀        alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or        C₇-C₄₀-arylalkyl radical optionally containing heteroatoms        belonging to groups 13-17 of the Periodic Table of the Elements;        preferably R⁴ is a hydrogen atom a C₁-C₁₀-alkyl or a C₆-C₄₀-aryl        radical;    -   W is an aromatic 5 or 6 membered ring that can contain        heteroatoms belonging to groups 15-16 of the Periodic Table of        the Elements; the valence of each atom of said ring is        substituted with hydrogen atom or it can optionally be        substituted with R⁵ groups, wherein R⁵, equal to or different        from each other, are C₁-C₄₀ hydrocarbon radicals optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; preferably R⁵, are linear or branched,        cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,        C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radicals        optionally containing heteroatoms belonging to groups 13-17 of        the Periodic Table of the Elements;    -   Preferably W is selected from the group comprising the following        moieties of formula (Wa), (Wb) and (Wc):

-   -   wherein the * represents the point in which the moiety bounds        the indenyl moiety of the compound of formula (I);    -   R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal to or different from each other,        are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; preferably R⁶, R⁷, R⁸, R⁹ and R¹⁰, are        hydrogen atoms or linear or branched, cyclic or acyclic,        C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,        C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radicals optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements;    -   Z¹ is a nitrogen atom or a CR¹⁰ group; Z² is a nitrogen atom or        a CR⁶ group; Z³ is a nitrogen atom or a CR⁷ group; Z⁴ is a        nitrogen atom or a CR⁸ group; Z⁵ is a nitrogen atom or a CR⁹        group; provided that not more that 2 groups among Z¹, Z², Z³, Z⁴        and Z⁵ are nitrogen atoms, preferably not more that one group        among Z¹, Z², Z³, Z⁴ and Z⁵ is a nitrogen atom;    -   Z⁶ is an oxygen atom, a sulfur atom, a NR¹³ group or a CR¹³        group; Z⁷ is an oxygen atom, a sulfur atom, a NR¹⁴ group or a        CR¹⁴ group; Z⁸ is an oxygen atom, a sulfur atom, a NR¹⁵ group or        a CR¹⁵ group; Z⁹ is an oxygen atom, a sulfur atom, a NR¹⁶ group        or a CR¹⁶ group;    -   Z¹⁰ is a nitrogen atom or a carbon atom that bonds the indenyl        moiety of the structure of formula (I); with the proviso that        not more than 1 group among Z⁶, Z⁷, Z⁸, Z⁹ or Z¹⁰ is a sulfur        atom, an oxygen atom or a nitrogen-containing group atom        selected from NR¹³, NR¹⁴, NR¹⁵, NR¹⁶, and a nitrogen atom;    -   R¹³, R¹⁴, R¹⁵ and R¹⁶, equal to or different from each other,        are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; preferably R⁶, R⁷, R⁸, R⁹ and R¹⁰, are        hydrogen atoms or linear or branched, cyclic or acyclic,        C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,        C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radicals optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; more preferably R⁶, R⁷, R⁸, R⁹ and R¹⁰        are hydrogen atoms, C₁-C₄₀-alkyl or C₆-C₄₀-aryl radicals;    -   In the moiety of formula (Wa), in a preferred embodiment, R⁷ is        a C₁-C₄₀-alkyl radical, preferably a branched C₁-C₄₀-alkyl        radical such as a tertbutyl radical, more preferably R⁷ is a        branched C₁-C₄₀-alkyl radical wherein the carbon atom in        position alpha is a tertiary carbon atom and R⁶, R⁸, R⁹ and R¹⁰        are hydrogen atoms;    -   in a further preferred embodiment R¹⁰ and R⁸ are C₁-C₄₀-alkyl        radicals, preferably they are linear C₁-C₄₀ alkyl radicals such        as methyl radicals and R⁷ and R⁹ are hydrogen radicals;    -   in a further preferred embodiment R⁶, R⁷ and R⁸ are linear or        branched C₁-C₄₀-alkyl radicals such as methyl or tertbutyl        radicals and R¹⁰ and R⁹ are hydrogen atoms;    -   in a further preferred embodiment R⁶, R⁷, R⁸, R⁹ and R¹⁰ are        hydrogen atoms;    -   in the moiety of formula (Wb), in a preferred embodiment, Z¹ is        a nitrogen atom and Z², Z³, Z⁴ and Z⁵ are respectively CR⁶, CR⁷,        CR⁸ and CR⁹ wherein the meaning of R⁶, R⁷, R⁸, and R⁹ is        described above; in a further preferred embodiment Z³ is a        nitrogen atom and Z¹, Z², Z⁴ and Z⁵ are respectively CR¹⁰, CR⁶,        CR⁸ and CR⁹ wherein the meaning of R¹⁰, R⁶, R⁸, and R⁹ is        described above; in a further preferred embodiment Z² is a        nitrogen atom and Z¹, Z³, Z⁴ and Z⁵ are respectively CR¹⁰, CR⁷,        CR⁸ and CR⁹ wherein the meaning of R¹⁰, R⁷, R⁸, and R⁹ is        described above;    -   in the moiety of formula (Wc) in a preferred embodiment Z⁶ is an        oxygen atom, a sulfur atom, a NR¹⁶ group; preferably it is a        sulfur atom or a NR¹⁶; wherein R¹⁶ is preferably a C₁-C₄₀-alkyl        radical; more preferably Z⁶ is a sulfur atom; and Z⁷, Z⁸, Z⁹ and        Z¹⁰ are respectively a CR¹⁴, CR¹⁵, CR¹⁶ and a carbon atom,        wherein R¹⁴ is a hydrogen atom or a C₁-C₄₀-alkyl radical such as        methyl or ethyl; and R¹⁵ and R¹⁶ are hydrogen atoms or        C₁-C₄₀-alkyl radicals.

A further preferred class of compounds of formula (I) has formula (IIa),(IIb), or (IIc):

Wherein M, L, X, R¹, R⁴, R⁶, R⁷, R⁸, R⁹ and R¹⁰ have the meaningreported above and R¹¹ and R¹² equal to or different from each other,are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; preferably R¹¹ and R¹² are hydrogen atoms or linear orbranched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl radicals, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements; more preferably R¹¹ and R¹²are hydrogen atoms or C₁-C₁₀-alkyl radicals such as methyl or ethylradicals. Preferably the metallocene compounds of formula (I) have C₂symmetry. Metallocene symmetry classes can be found on Resconi et al.Chemical Reviews, 2000, Vol. 100, No. 4 1263 and references hereincited.

Preferably the metallocene compounds to be used in the process of thepresent invention are in their racemic(rac) or racemic-like form.Racemic(rac) and racemic-like form are described in PCT/EP2005/052688.

Examples of compounds having formula (I) are as follows

-   Me₂Si(6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si[6-Me-4-(4-t-BuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂,-   Me₂Si(6,8-Me2-4-(4-t-BuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si[6-Me-4-(2-MePh)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂,-   Me₂Si(6,8-Me2-4-(2-MePh)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(1,1,3,3,6-Me5-4-(2-MePh)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si[6-Me-4-(2,5-Me₂Ph)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂,-   Me₂Si[6-Me-4-(4-biphenyl)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂,-   Me₂Si(1,1,3,3,6-Me5-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si[1,1,3,3,6-Me5-4-(4-tBuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂,-   Me₂Si(2,2,6-Me3-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(2-Me-4-Ph-1H-cyclopenta[b]naphthalen-1-yl)₂ZrCl₂,-   Me₂Si(2,5,8-Me3-4-Ph-1H-cyclopenta[b]naphthalen-1-yl)₂ZrCl₂,-   Me₂Si(2-Me-4-Ph-5,6,7,8-tetrahydro-1H-cyclopenta[b]naphthalen-1-yl)₂ZrCl₂,-   Me₂Si(2,6-Me2-4-Ph-5H-1-thia-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(2,3,6-Me3-4-Ph-5H-1-thia-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(2,6-Me2-4-(4-t-BuPh)-5H-1-thia-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(2,3,6-Me3-4-(4-t-BuPh)-5H-1-thia-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(2-Me-4-Ph-1,5,6,7,8,9-hexahydrocyclohepta[f]    inden-1-yl)₂ZrCl₂,-   Me₂Si(6-Me-4-(2-benzothiophenyl)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(6-Me-4-(2-(5-methylthiophenyl))-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(6-Me-4-(2-(5-methylfuryl))-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Me₂Si(6-Me-4-(4-pyridyl)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   C₂H₄(6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   C₂H₄(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Ph₂Si(6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂,-   Ph₂Si(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂-   Me₂Si(6-Me-4-(2-(5-methylthiophenyl))-1,2,3,5-tetrahydro-s-indacen-7-yl)    (6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)ZrCl₂-   Me₂Si(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)    (6-Me-4-(4-t-BuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl) ZrCl₂    -   and their correspondent dimethyl derivatives.

The process of the present invention is preferably carried out at atemperature ranging from 60° C. to 200° C., more preferably at atemperature ranging from 70° C. to 150° C., even more preferably from80° C. to 120° C.

The alumoxanes used in the process according to the invention areconsidered to be linear, branched or cyclic compounds containing atleast one group of the type:

wherein the substituents U, same or different, are defined above.

In particular, alumoxanes of the formula:

can be used in the case of linear compounds, wherein n¹ is 0 or aninteger of from 1 to 40 and the substituents U are defined as above; oralumoxanes of the formula:

can be used in the case of cyclic compounds, wherein n2 is an integerfrom 2 to 40 and the U substituents are defined as above.

Examples of alumoxanes suitable for use according to the presentinvention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO),tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO),tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) andtetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

Particularly interesting cocatalysts are those described in WO 99/21899and in WO01/21674 in which the alkyl and aryl groups have specificbranched patterns.

Non-limiting examples of aluminium compounds that can be reacted withwater to give suitable alumoxanes (b), described in WO 99/21899 andWO01/21674, are: tris(2,3,3-trimethyl-butyl)aluminium,tris(2,3-dimethyl-hexyl)aluminium, tris(2,3-dimethyl-butyl)aluminium,tris(2,3-dimethyl-pentyl)aluminium, tris(2,3-dimethyl-heptyl)aluminium,tris(2-methyl-3-ethyl-pentyl)aluminium,tris(2-methyl-3-ethyl-hexyl)aluminium,tris(2-methyl-3-ethyl-heptyl)aluminium,tris(2-methyl-3-propyl-hexyl)aluminium,tris(2-ethyl-3-methyl-butyl)aluminium,tris(2-ethyl-3-methyl-pentyl)aluminium,tris(2,3-diethyl-pentyl)aluminium,tris(2-propyl-3-methyl-butyl)aluminium,tris(2-isopropyl-3-methyl-butyl)aluminium,tris(2-isobutyl-3-methyl-pentyl)aluminium,tris(2,3,3-trimethyl-pentyl)aluminium,tris(2,3,3-trimethyl-hexyl)aluminium,tris(2-ethyl-3,3-dimethyl-butyl)aluminium,tris(2-ethyl-3,3-dimethyl-pentyl)aluminium,tris(2-isopropyl-3,3-dimethyl-butyl)aluminium,tris(2-trimethylsilyl-propyl)aluminium,tris(2-methyl-3-phenyl-butyl)aluminium,tris(2-ethyl-3-phenyl-butyl)aluminium,tris(2,3-dimethyl-3-phenyl-butyl)aluminium,tris(2-phenyl-propyl)aluminium,tris[2-(4-fluoro-phenyl)-propyl]aluminium,tris[2-(4-chloro-phenyl)-propyl]aluminium,tris[2-(3-isopropyl-phenyl)-propyl]aluminium,tris(2-phenyl-butyl)aluminium, tris(3-methyl-2-phenyl-butyl)aluminium,tris(2-phenyl-pentyl)aluminium,tris[2-(pentafluorophenyl)-propyl]aluminium,tris[2,2-diphenyl-ethyl]aluminium andtris[2-phenyl-2-methyl-propyl]aluminium, as well as the correspondingcompounds wherein one of the hydrocarbyl groups is replaced with ahydrogen atom, and those wherein one or two of the hydrocarbyl groupsare replaced with an isobutyl group.

Amongst the above aluminium compounds, trimethylaluminium (TMA),triisobutylaluminium (TIBA), tris(2,4,4-trimethyl-pentyl)aluminium(TIOA), tris(2,3-dimethylbutyl)aluminium (TDMBA) andtris(2,3,3-trimethylbutyl)aluminium (TTMBA) are preferred.

Non-limiting examples of compounds able to form an alkylmetallocenecation are compounds of formula D⁺E⁻, wherein D⁺ is a Brønsted acid,able to donate a proton and to react irreversibly with a substituent Xof the metallocene of formula (I) and E⁻ is a compatible anion, which isable to stabilize the active catalytic species originating from thereaction of the two compounds, and which is sufficiently labile to beremoved by an olefinic monomer. Preferably, the anion E⁻ comprises oneor more boron atoms. More preferably, the anion E⁻ is an anion of theformula BAr₄ ⁽⁻⁾, wherein the substituents Ar which can be identical ordifferent are aryl radicals such as phenyl, pentafluorophenyl orbis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate isparticularly preferred compound, as described in WO 91/02012. Moreover,compounds of formula BAr₃ can be conveniently used. Compounds of thistype are described, for example, in the International patent applicationWO 92/00333. Other examples of compounds able to form analkylmetallocene cation are compounds of formula BAr₃P wherein P is asubstituted or unsubstituted pyrrol radical. These compounds aredescribed in WO01/62764. Compounds containing boron atoms can beconveniently supported according to the description of DE-A-19962814 andDE-A-19962910. All these compounds containing boron atoms can be used ina molar ratio between boron and the metal of the metallocene comprisedbetween about 1:1 and about 10:1; preferably 1:1 and 2.1; morepreferably about 1:1.

Non limiting examples of compounds of formula D⁺E⁻ are:

-   Tributylammonium tetrakis(pentafluorophenyl)aluminate,-   Tributylammonium tetrakis(trifluoromethylphenyl)borate,-   Tributylammonium tetrakis(4-fluorophenyl)borate,-   N,N-Dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylhexylamoniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)aluminate,-   N,N-Dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylhexylamoniumtetrakis(pentafluorophenyl)borate,-   Di(propyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)aluminate,-   Ferroceniumtetrakis(pentafluorophenyl)borate,-   Ferroceniumtetrakis(pentafluorophenyl)aluminate.-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate, and-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate.

Additional examples of compounds of formula D⁺E⁻ that can be usedaccording to the present invention are described in WO 04/005360, WO02/102811 and WO 01/62764.

Organic aluminum compounds used as compound c) are those of formulaH_(j)AIU_(3-j) or H_(j)Al₂U_(6-j) as described above.

The catalyst system of the present invention can be prepared bycontacting the metallocene of formula (I) and a suitable cocatalyst, ina solvent. The cocatalyst is preferably the reaction product ofmethylalumoxane and triisobutylaluminum.

The catalyst of the present invention can be preferably preparedaccording to PCT/EP2005/002479 both by distilling off toluene or byfollowing the described procedure but without such a distillation. Thecatalysts of the present invention can also be supported on an inertcarrier. This is achieved by depositing the metallocene compound a) orthe product of the reaction thereof with the component b), or thecomponent b) and then the metallocene compound a) on an inert support.The support can be a porous solid such as talc, a sheet silicate, aninorganic oxide or a finely divided polymer powder (e.g. polyolefin).Suitable inorganic oxides may be found among the oxides of elements ofgroups 2, 3, 4, 5, 13, 14, 15 and 16 of the Periodic Table of theElements. Examples of oxides preferred as supports include silicondioxide, aluminum oxide, and also mixed oxides of the elements calcium,aluminum, silicon, magnesium or titanium and also corresponding oxidemixtures, magnesium halides, styrene/divinylbenzene copolymers,polyethylene or polypropylene. Other inorganic oxides which can be usedalone or in combination with the above-mentioned preferred oxidicsupports are, for example, MgO, ZrO₂, TiO₂ or B₂O₃.

A suitable class of supports which can be used is that constituted byporous organic supports functionalized with groups having activehydrogen atoms. Particularly suitable are those in which the organicsupport is a partially crosslinked styrene polymer. Supports of thistype are described in European application EP-633 272.

Another class of inert supports particularly suitable for use accordingto the invention is that of polyolefin porous prepolymers, particularlypolyethylene.

A further suitable class of inert supports for use according to theinvention is that of porous magnesium halides such as those described inInternational application WO 95/32995.

The support materials used preferably have a specific surface area inthe range from 10 to 1 000 m²/g, a pore volume in the range from 0.1 to5 ml/g and a mean particle size of from 1 to 500 μm. Preference is givento supports having a specific surface area in the range from 50 to 500m²/g, a pore volume in the range from 0.5 to 3.5 ml/g and a meanparticle size in the range from 5 to 350 μm. Particular preference isgiven to supports having a specific surface area in the range from 200to 400 m²/g, a pore volume in the range from 0.8 to 3.0 ml/g and a meanparticle size of from 10 to 300 μm.

The inorganic support can be subjected to a thermal treatment, e.g. toremove adsorbed water. Such a drying treatment is generally carried outat from 80 to 300° C., preferably from 100 to 200° C., with drying atfrom 100 to 200° C. preferably being carried out under reduced pressureand/or a blanket of inert gas (e.g. nitrogen), or the inorganic supportcan be calcined at from 200 to 1000° C. to produce the desired structureof the solid and/or set the desired OH concentration on the surface. Thesupport can also be treated chemically using customary desiccants suchas metal alkyls, preferably aluminum alkyls, chlorosilanes or SiCl₄, orelse methylaluminoxane. Appropriate treatment methods are described, forexample, in WO 00/31090.

The inorganic support material can also be chemically modified. Forexample, treatment of silica gel with (NH₄)₂SiF₆ leads to fluorinationof the silica gel surface, or treatment of silica gels with silanescontaining nitrogen-, fluorine- or sulfur-containing groups leads tocorrespondingly modified silica gel surfaces.

Organic support materials such as finely divided polyolefin powders(e.g. polyethylene, polypropylene or polystyrene) can also be used andare preferably likewise freed of adhering moisture, solvent residues orother impurities by means of appropriate purification and dryingoperations before use. It is also possible to use functionalized polymersupports, e.g. supports based on polystyrene, via whose functionalgroups, for example carboxylic or hydroxy groups, at least one of thecatalyst components can be immobilized. The solid compound obtained bysupporting the catalyst system object of the present invention on acarrier in combination with the further addition of the alkylaluminiumcompound either as such or prereacted with water if necessary.

In a preferred embodiment the polymerization process of the presentinvention is carried out in solution.

For the purpose of the present invention the term solutionpolymerization means that the polymer is fully soluble in thepolymerization medium at the polymerization temperature used, and in aconcentration range of at least 5% by weight; preferably from 5 to 50%by weight.

In order to have the polymer completely soluble in the polymerizationmedium, a mixtures of monomers in the presence of an inert solvent canbe used. This solvent can be an aliphatic or cycloaliphatic hydrocarbonsuch as hexane, heptane, isooctane, isododecane, cyclohexane andmethylcyclohexane. It is also possible to use mineral spirit or ahydrogenated diesel oil fraction. Also aromatic hydrocarbons can be usedsuch as toluene. Preferred solvents to be used are cyclohexane andmethylcyclohexane. The 1-butene or alpha-olefin content in the mixturecan be varied according to the final comonomer content wished in thecopolymer and the relative reactivity ratio of the comonomers. Theethylene content in the liquid phase of the polymerization mediumpreferably ranges from 1% to 10% by weight; more preferably from 2% to8% by weight.

The ratio of the comonomers varies accordingly, depending on the wishedfinal copolymer and the relative comonomers reactivity ratio of thecatalyst system.

The skilled man is able to select the ratio of ethylene and comonomer inorder to obtain the whished copolymer.

The copolymers obtained according to the process of the presentinvention, especially those having high comonomer content, are verysticky, this makes it difficult to produce in an industrial plant whenthe polymerization process is carried out in slurry or in gas phasebecause of the fouling in the reactor. On the contrary when a solutionpolymerization process is carried this problem is avoided.

According to the process of the present invention ethylene is contactedwith at least an alpha olefin of formula CH₂═CHA wherein T is a C₂-C₂₀alkyl radical. Examples of alpha olefin of formula CH₂═CHT are 1-butene,1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene,4,6-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene and 1-eicosene. Preferred comonomer to beused 1-butene, and 1-hexene.

The content of ethylene derived units in the copolymers obtainedaccording to the present invention ranges preferably from 60% by mol to95% by mol. Preferably the content of ethylene derived units ranges from75% by mol to 95% by mol.

The molecular weight can be very effectively controlled by the additionof hydrogen.

The molecular weight distribution can be varied by using mixtures ofdifferent metallocene compounds or by carrying out the polymerization inseveral stages which differ as to the polymerization temperature and/orthe concentrations of the molecular weight regulators and/or themonomers concentration. Moreover by carrying out the polymerizationprocess by using a combination of two different metallocene compounds apolymer endowed with a broad melting is produced.

The polymer obtained according to the process of the present inventioncan further contain up to 10% by mol of a non conjugated diene. Nonconjugated dienes can be a straight chain, branched chain or cyclichydrocarbon diene having from 6 to 20 carbon atoms. Examples of suitablenon-conjugated dienes are:

-   -   straight chain acyclic dienes, such as 1,4-hexadiene and        1,6-octadiene;    -   branched chain acyclic dienes, such as 5-methyl-1,4-hexadiene,        3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene and mixed        isomers of dihydro myricene and dihydroocinene;    -   single ring alicyclic dienes, such as 1,3-cyclopentadiene,        1,4-cyclohexadiene, 1,5-cyclooctadiene and 1,5-cyclododecadiene;    -   multi-ring alicyclic fused and bridged ring dienes, such as        tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene,        bicyclo-(2,2,1)-hepta-2,5-diene; and    -   alkenyl, alkylidene, cycloalkenyl and cycloalkylidene        norbornenes, such as 5-methylene-2-norbornene (MNB),        5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,        5-(4-cyclopentenyl)-2-norbornene,        5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and        norbornadiene.

Preferred dienes are 1,4-hexadiene (HD), 5-ethylidene-2-norbornene(ENB), 5-vinylidene-2-norbornene (VNB), 5-methylene-2-norbornene (MNB)and dicyclopentadiene (DCPD). Particularly preferred dienes are5-ethylidene-2-norbornene (ENB) and 1,4-hexadiene (HD).

When present the non-conjugated dienes are preferably incorporated intothe polymer in an amount from 0.1% to about 10% by mol, preferably from0.2% to 5% by mol, and more preferably from 0.3% to 3% by mol. Ifdesired, more than one diene may be incorporated simultaneously, forexample HD and ENB, with total diene incorporation within the limitsspecified above.

Therefore a further object of the present invention is a polymerizationprocess comprising contacting under polymerization conditions ethylene,an alpha olefin of formula CH₂═CHA and a non conjugated diene, in thepresence of a catalyst system obtainable by contacting:

-   -   b) at least a metallocene compound of formula (I)

-   -   b) alumoxane or a compound capable of forming an alkyl        metallocene cation; and optionally    -   c) an organo aluminum compound.

Preferably the process is carried out in solution.

The following examples are given to illustrate and not to limit theinvention.

EXAMPLES General Characterization Intrinsic Viscosity (IV) inTetrahydronaphthalene

The measurement were done in tetrahydronaphthalene (THN) solutionobtained by dissolving the polymer at 135° C. for 1 hour.

¹³C-NMR Analysis of Ethylene-Butene Copolymers

The polymer microstructure was investigated by ¹³C-NMR analysis. Thesamples were dissolved with a 8% wt/v concentration in1,1,2,2-tetrachloroethane-d₂ at 120° C. The ¹³C-NMR spectra wereacquired at 120° C. on a Bruker DPX400 spectrometer operating at 100.61MHz. Each spectrum was acquired with a 90° pulse, 15 seconds of delaybetween pulses and CPD (WALTZ 16) to remove ¹H-¹³C coupling. About 1500transients were stored in 32K data points using a spectral window of6000 Hz.

The assignments of the peaks were made according to Randall[1] and thetriad distribution and copolymer compositions was determined accordingto the method proposed by Kakugo.[2] (taking into account peakaverlapping).

The Tβδ peak at 37.24 ppm (nomenclature according to reference 3) wasused as internal reference. The product of reactivity ratios r₁×r₂ wascalculated from the triads according to Carman.[3]

-   [1] J. C. Randall, Macromol. Chem. Phys. 1989, C29, 201.-   [2] M. Kakugo, Y. Naito, K. Mizunuma, T. Miyatake, Macromolecules    1982, 15, 1150.-   [3] C. J. Carman, R. A. Harrington, C. E. Wilkes. Macromolecules    1977, 10, 535.

Chemicals and Characterization.

All chemicals were handled using standard Schlenk techniques.Methylalumoxane (MAO) was received from Albemarle as a 30% wt/wt toluenesolution and used as such.

Racemic-dimethylsilylbis(2-methyl-4-(4-tert-butyl-phenyl)-inden-1-yl)dichlorozirconiumC-1 was prepared according to WO 98/40331 (example 65);racemic-dimethylsilylbis(2-methyl-4-(4-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl)dichlorozirconiumA-1 was prepared according to the procedure described in EP05102189.7.

Catalyst Systems Preparation of the Catalyst Systems. Catalyst System S1

900 g of TIBA/cyclohexane solution (332 g/L), 1070 mL of MAO/toluenesolution (Albemarle 30% wt/wt, d=0.92 g/mL) and 1600 g of cyclohexanewere mixed in a 12 L thermostated autoclave. After 1 h of stirring at50° C., 9.67 g of A-1 (previously suspended in 60 mL of toluene) wereadded to the MAO/TIBA solution. The resulting mixture was stirred foradditional 90 min at 50° C., then 4400 g of cyclohexane were added andafter additional 10 min stirring, the mixture was filtered to finallygive a red solution (concentration=76 g_(TOT)/L and 0.97g_(metallocene)/L).

Catalyst System S2

13.5 mL of TIBA/cyclohexane solution (113 g/L) were mixed with 3.2 mL ofMAO/toluene solution (Albemarle 30% wt/wt, d=0.92 g/mL, 15.3 mmol MAO)to obtain a MAO/TIBA molar ratio of 2:1. The solution was stirred for 1h at room temperature and transferred into a 50 mL Schlenk flaskcontaining C-1 (28.4 mg, 38.3 μmol). The final solution was diluted with7.7 mL of cyclohexane. Final mixture concentration=100 g_(TOT)/L and1.165 g_(metallocene)/L; color=dark red solution.

Polymerization Tests.

The amount of monomers (respectively C₁ and C₂) and solvent initiallycharged into the autoclave, and the ratio of the two monomers constantlyfed during the test were calculated via ASPEN ONE simulation, based onthe desired composition for the final copolymer and on the reactivityratio R of a given metallocene:

$R = {\frac{\left( {C_{1}/C_{2}} \right)_{polymer}}{\left( {C_{1}/C_{2}} \right)_{liquidphase}} = \frac{F}{f}}$

Ethylene-1-butene Copolymerization Tests Comparative Example 1

A 4.4 L jacketed stainless-steel autoclave, equipped with a mechanicalstirrer and a 50-mL stainless-steel vial, was purified by washing withan Al(1-Bu)₃ solution in hexane and dried at 70° C. in a stream ofnitrogen.

11.9 mL of a 100 g/L Al(i-Bu)₃/hexane solution (corresponding to 6 mmolof Al(i-Bu)₃), 1000 g of cyclohexane, 111.5 g of ethylene and 121.6 g ofbutene were charged into the autoclave, and heated to 100° C., thusproducing a liquid composition of 15/85 (wt/wt) monomers/cyclohexane,and a pressure of 22 bar-g.

2 mL of the catalyst system S2 containing the catalyst/cocatalystmixture (1.165 mg metallocene/mL solution) were diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 60/40% wt was continuously fed for 30minutes to maintain the pressure at 22 bar-g for a total consumption of19 g of ethylene and 12 g of butene.

The autoclave was pressurized with nitrogen up to 30 bar, the bottomdischarge valve opened and the polymer discharged into a heated steeltank and treated for 10 min with water steam. The tank heating wasswitched off and a flow of nitrogen at 0.5 bar-g was fed to remove thewater. The steel tank was finally opened, the wet polymer collected, anddried overnight under reduced pressure at 70° C. The results of theanalysis performed on the polymer samples are reported in Table 1.

Comparative Example 2

The procedure of comparative example 1 was repeated feeding 1000 g ofcyclohexane, 143.7 g of ethylene, and 101 g of butene in order toobtain, at 100° C. and 28 bar-g, a liquid composition of 15/85% wtmonomers/cyclohexane.

2.5 mL of the catalyst system S2 containing the catalyst/cocatalystmixture (1.165 mg metallocene/mL solution) were diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 70/30% wt was continuously fed for 30minutes to maintain the pressure of 28 bar-g: 33.4 g of ethylene and14.2 g of butene were consumed. The results of the analysis performed onthe polymer samples are reported in Table 1.

Comparative Example 3

The procedure of comparative example 1 was repeated feeding 1000 g ofcyclohexane, 183 g of ethylene, and 75 g of butene in order to obtain,at 100° C. and 32 bar-g, a liquid composition of 15/85% wtmonomers/cyclohexane.

3 mL of the catalyst system S2 containing the catalyst/cocatalystmixture (1.165 mg metallocene/mL solution) were diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 80/20% wt was continuously fed for 30minutes to maintain the pressure of 32 bar-g: 110 g of ethylene and 28.4g of butene were consumed. The results of the analysis performed on thepolymer samples are reported in Table 1.

Example 4

The procedure of comparative example 1 was repeated feeding 1000 g ofcyclohexane, 170 g of ethylene, and 84 g of butene in order to obtain,at 100° C. and 31 bar-g, a liquid composition of 15/85% wtmonomers/cyclohexane.

1 mL of the catalyst system SI containing the catalyst/cocatalystmixture (0.97 mg metallocene/mL solution) was diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 80/20% wt was continuously fed for 30minutes to maintain the pressure of 32 bar-g: 74.9 g of ethylene and18.5 g of butene were consumed. The results of the analysis performed onthe polymer samples are reported in Table 1.

Example 5

The procedure of comparative example 1 was repeated feeding 1000 g ofcyclohexane, 55.2 g of ethylene, and 158 g of butene in order to obtain,at 100° C. and 15 bar-g, a liquid composition of 15/85% wtmonomers/cyclohexane. 400 normal mL of hydrogen were charged through astainless-steel cylinder equipped with a pressure gauge and connected tothe autoclave.

0.5 mL of the catalyst system S1 containing the catalyst/cocatalystmixture (0.97 mg metallocene/mL solution) were diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 60/40% wt was continuously fed for 30minutes to maintain the pressure of 15 bar-g: 52 g of ethylene and 35 gof butene were consumed. The results of the analysis performed on thepolymer samples are reported in Table 1.

Example 6

The procedure of comparative example 1 was repeated feeding 1091 g ofcyclohexane, 187 g of ethylene, and 250 g of butene in order to obtain,at 100° C. and 34 bar-g, a liquid composition of 25/75% wtmonomers/cyclohexane. 300 normal mL of hydrogen were charged through astainless-steel cylinder equipped with a pressure gauge and connected tothe autoclave. 0.5 mL of the catalyst system SI containing thecatalyst/cocatalyst mixture (0.97 mg metallocene/mL solution) werediluted with 5 mL of cyclohexane, charged in the stainless-steel vialand injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 80/20% wt was continuously fed for 30minutes to maintain the pressure of 15 bar-g: 47.7 g of ethylene and11.6 g of butene were consumed. The results of the analysis performed onthe polymer samples are reported in Table 1.

Example 7

The procedure of comparative example 1 was repeated feeding 901 g ofcyclohexane, 175 g of ethylene, and 405 g of butene in order to obtain,at 100° C. and 33 bar-g, a liquid composition of 36/64% wtmonomers/cyclohexane. 300 normal mL of hydrogen were charged in theautoclave.

0.5 mL of the catalyst system SI containing the catalyst/cocatalystmixture (0.97 mg metallocene/mL solution) were diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 70/30% wt was continuously fed for 30minutes to maintain the pressure of 33 bar-g: 17.7 g of ethylene and 7.6g of butene were consumed. The results of the analysis performed on thepolymer samples are reported in Table 1.

Example 8

The procedure of comparative example 1 was repeated feeding 664 g ofcyclohexane, 163 g of ethylene, and 585 g of butene in order to obtain,at 100° C. and 34 bar-g, a liquid composition of 50/50% wtmonomers/cyclohexane. 300 normal mL of hydrogen were charged in theautoclave.

1 mL of the catalyst system SI containing the catalyst/cocatalystmixture (0.97 mg metallocene/mL solution) was diluted with 5 mL ofcyclohexane, charged in the stainless-steel vial and injected into theautoclave by nitrogen overpressure.

A constant ethylene/butene mixture 60/40% wt was continuously fed for 30minutes to maintain the pressure of 34 bar-g: 39 g of ethylene and 26.4g of butene were consumed. The results of the analysis performed on thepolymer samples are reported in Table 1.

TABLE l Catalyst H₂ Yield kg_(POL)/ I.V. Ethylene from Ethylene fromExample System (mL) (g) (g_(met)*30′) (dL/g, THN) NMR (% wt) NMR (% mol)1* S2 0 10 4.4 2.00 73.6 84.8 2* S2 0 27 9.4 2.43 81.1 89.6 3* S2 0 246.9 2.47 88.6 94.0 4 S1 0 106 109 4.90 89.6 94.5 5 S1 400 100 205 0.8461.5 76.1 6 S1 300 74 153 3.53 83.3 90.9 7 S1 300 38 78 2.51 73.0 84.4 8S1 300 65 67 2.22 64.1 78.1 *comparative examples

1-10. (canceled)
 11. A polymerization process comprising contactingunder polymerization conditions ethylene and at least one alpha olefinof formula CH2=CHA, wherein A is a C₂-C₂₀ alkyl radical, to obtain acopolymer comprising from 95% by mol to 50% by mol of ethylene derivedunits in presence of a catalyst system obtained by contacting: a) atleast a metallocene compound of formula (I)

and b) alumoxane or a compound capable of forming an alkyl metallocenecation; wherein: M is an atom of a transition metal selected from group3, 4, or the lanthanide or actinide groups in the Periodic Table ofElements; X equal to or different from each other, is hydrogen, halogen,R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂; R is a linear or branched,cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical, optionallycomprising at least one heteroatom belonging to groups 13-17 of thePeriodic Table of Elements; R′ is a C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene,C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylidene radical; L is a divalentbridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀ cycloalkylidene,C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, or C₇-C₂₀ arylalkylideneradicals, optionally comprising at least one heteroatom belonging togroups 13-17 of the Periodic Table of Elements, or a silylidene radicalcomprising up to 5 silicon atoms; R¹ is a linear C₁-C₄₀ hydrocarbonradical optionally comprising at least one heteroatom belonging togroups 13-17 of the Periodic Table of Elements; R₂ and R₃ equal to ordifferent from each other, are C₁-C₄₀ hydrocarbon radicals optionallycomprising at least one heteroatom belonging to groups 13-17 of thePeriodic Table of Elements, or R₂ and R₃ are part of 4-7 membered ringcondensed to the benzene ring of the indenyl moiety, the ring optionallycomprising at least one heteroatom belonging to groups 13-16 of thePeriodic Table of Elements, wherein the valence of each atom forming thering being filled with R¹⁸ radicals; R¹⁸ equal to or different from eachother, are hydrogen or C₁-C₄₀ hydrocarbon radicals; R⁴ is hydrogen or aC₁-C₄₀ hydrocarbon radical optionally comprising at least one heteroatombelonging to groups 13-17 of the Periodic Table of Elements; W is anaromatic 5 or 6 membered ring optionally comprising at least oneheteroatom belonging to groups 13-16 of the Periodic Table of Elements,wherein the valence of each atom of the ring is substituted with hydrogeor is optionally substituted with at least one R⁵ group; and R⁵ equal toor different from each other, are C₁-C₄₀ hydrocarbon radicals optionallycomprising at least one heteroatom belonging to groups 13-17 of thePeriodic Table of Elements.
 12. The process according to claim 11,wherein R¹ is methyl, ethyl, an alpha branched aryl, or an arylalkylradical comprising from 2 to 20 carbon atoms optionally comprising atleast one O, N, S, P and Se atom.
 13. The process according to claim 11,wherein the catalyst system further comprises c) an organo aluminumcompound.
 14. The process according to claim 11, wherein M is zirconium,titanium or hafnium; X is hydrogen, halogen, OR′O or R group; L isSi(R¹¹)₂; R¹¹ is a linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl,C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl orC₇-C₄₀-arylalkyl radical; and R¹ is a C₁-C₁₀-alkyl radical.
 15. Theprocess according to claim 11, wherein R² and R³ are part of 5-6membered ring condensed to the benzene ring of the indenyl moiety, thering being substituted with R¹⁸ radicals; R¹⁸ is hydrogen or a linear orbranched, C₁-C₂₀-alkyl radical; and R⁴ is hydrogen, a C₁-C₁₀-alkyl, or aC₆-C₄₀-aryl radical.
 16. The process according to claim 11, wherein W isselected from the group comprising the following moieties of formula(Wa), (Wb) and (Wc):

wherein the * represents the point in which the moiety is bound to theindenyl moiety of the compound of formula (I); R⁶, R⁷, R⁸, R⁹ and R¹⁰,equal to or different from each other, are hydrogen or C₁-C₄₀hydrocarbon radicals optionally comprising at least one heteroatombelonging to groups 13-17 of the Periodic Table of Elements; Z¹ isnitrogen or a CR¹⁰ group; Z² is nitrogen or a CR⁶ group; Z³ is nitrogenor a CR⁷ group; Z⁴ is nitrogen or a CR⁸ group; Z⁵ is nitrogen or a CR⁹group, with the proviso that not more that 2 groups among Z¹, Z², Z³, Z⁴and Z⁵ are nitrogen atoms; Z⁶ is oxygen, sulfur, a NR¹³ group or a CR¹³group; Z⁷ is oxygen, sulfur, a NR⁴ group or a CR⁴ group; Z⁸ is oxygen,sulfur, a NR¹⁵ group or a CR¹⁵ group; Z⁹ is oxygen, sulfur, a NR¹⁶ groupor a CR¹⁶ group; Z¹⁰ is nitrogen or carbon, with the proviso that notmore than 1 group among Z⁶, Z⁷, Z⁸, Z⁹ or Z¹⁰ is sulfur, oxygen, or anitrogen-containing group selected from nitrogen, NR¹³, NR¹⁴, NR¹⁵, andNR¹⁶; and R¹³, R¹⁴, R¹⁵ and R¹⁶, equal to or different from each other,are hydrogen or C₁-C₄₀ hydrocarbon radicals optionally comprising atleast one heteroatom belonging to groups 13-17 of the Periodic Table ofElements.
 17. The process according to claim 11, wherein the compound offormula (I) comprises formula (IIa), (IIb) or (IIc):

wherein M is an atom of a transition metal selected from group 3, 4, orthe lanthanide or actinide groups in the Periodic Table of Elements; Xequal to or different from each other, is hydrogen, halogen, R, OR,OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂; R is a linear or branched, cyclicor acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical, optionally comprising atleast one heteroatom belonging to groups 13-17 of the Periodic Table ofElements; R′ is a C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene,C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylidene radical; L is a divalentbridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀ cycloalkylidene,C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, or C₇-C₂₀ arylalkylideneradicals, optionally comprising at least one heteroatom belonging togroups 13-17 of the Periodic Table of Elements, or a silylidene radicalcomprising up to 5 silicon atoms; R¹ is a linear C₁-C₄₀ hydrocarbonradical optionally comprising at least one heteroatom belonging togroups 13-17 of the Periodic Table of Elements; R⁴ is hydrogen or aC₁-C₄₀ hydrocarbon radical optionally comprising at least one heteroatombelonging to groups 13-17 of the Periodic Table of Elements; R⁵ equal toor different from each other, are C₁-C₄₀ hydrocarbon radicals optionallycomprising at least one heteroatom belonging to groups 13-17 of thePeriodic Table of Elements. R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal to ordifferent from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicalsoptionally comprising at least one heteroatom belonging to groups 13-17of the Periodic Table of Elements; R¹⁴, R¹⁵ and R¹⁶, equal to ordifferent from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicalsoptionally comprising at least one heteroatom belonging to groups 13-17of the Periodic Table of Elements; and R¹¹ and R¹² equal to or differentfrom each other, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicalsoptionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements.
 18. The process according to claim 11,wherein the process is carried out at a temperature ranging from 60° C.to 200° C.
 19. The process according to claim 11, wherein the processfurther comprises a polymerization medium comprising a mixture of liquidmonomers, optionally in presence of an aliphatic or cycloaliphatichydrocarbon solvent.
 20. The process according to claim 11, wherein thealpha olefins of formula CH2=CHA are 1-butene or 1-hexene.
 21. Theprocess according to claim 11, wherein the copolymer further comprisesup to 20% by mol of a non-conjugated diene.